498 SPECIAL PLANT PATHOLOGY 



spore horns or active perithecial pustules of Endothia parasitica. They 

 found that five of the twenty-one ants were carrying spores. Tests 

 with other insects demonstrated that they were carrying spores. The 

 number of viable spores carried varied from 74 to 336.960 per insect, 

 and the last number was obtained on Leptostylus Macula, one of the 

 beetles, which feeds on the pustules of the blight fungus. During 

 these experiments, it was proved that the spores of Endothia parasitica 

 were easily shaken from the body of the beetle during its own move- 

 ments. Heald and Studhalter^ undertook to determine whether birds 

 carried the spores. They found on birds shot on blighted chestnut 

 trees after the bill, head, tail, feet and wings of each bird were scrubbed 

 with a brush and poured plates were made from the wash water, which 

 was retained and centrifuged for its sediment, that in the case of the 

 36 birds tested, 19 were found to be carrying the spores of the chestnut- 

 blight fungus. The viable spores carried by two downy woodpeckers 

 numbered 757,074 and 642,341 respectively, while a brown creeper 

 carried 254,019, and that the highest positive results were obtained 

 from birds shot two to four days after a period of considerable rain- 

 fall. Analyses of spore traps at West Chester and Martic Forge^ 

 showed that viable pycnospores of the chestnut blight fungus were 

 washed down the trees in enormous numbers during every winter 

 rain. 



The mature stromata on older cankers have numerous projecting 

 papillae on the surface. The black speck at the tip of each papilla is 

 the opening of a perithecium, which is a bottle-shaped depression with 

 a long neck-like, black canal opening at the surface. There are com- 

 monly fifteen to thirty perithecia in a stroma. The mature perithecia 

 (Fig. 176) measure about 350 to 400^1 in diameter, and are mostly 

 spherical. The neck is usually four to six times the diameter of the 

 perithecium and its black wall is composed of densely interwoven, 

 septate, heavy-walled hyphae running parallel with the long axis of 

 the neck. The asci are clavate, or oblong, and contain eight ascospores 

 imbedded in an epiplasm. The ascospores are two celled and measure 



1 Heald, F. D. and Stud halter, R. A.: Birds as Carriers of the Chestnut Blight 

 Fungus. Journal of Agricultural Research II: 405-422, Sept. 21, 1914. 



2 Heald, F. D. and Gardner, M. W.: The Relative Prevalence of Pycnospores 

 and Ascospores of the Chestnut Blight Fungus during the Winter. Phytopathology 

 3: 296-305, December, 1913. 



